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CiMaC CongRess | SHAnGHAI 2013 For the two-stroke marine engines, lubrication of liners and piston rings has always been a field of high interest. Over the years the position and numbers of levels where the cylinder oil is injected, have been subject to many design variants. The issue regarding numbers and positions of the lubrication level is becoming an important subject with the new trend for two-stroke marine engines. The trend towards longer stroke/bore ratio will increase the distance from the injection level leading to longer ’road of transportation’ of the cylinder oil. A brief summary of lubrication systems used on MAN Diesel engines, and the basic functions of the cylinder oil will be given. The impact on the tribological system from the increased stroke will be discussed. In this paper, service tests with a lubrication level positioned very close to the TDC area is reported in details. The results are compared with a standard execution of the cylinder oil system. Wear measurements and drain oil analysis is used to analyse the effect of different modes of the test unit. In addition to the service test, a simulation of the cylinder oil performance is presented. Furthermore, the impact on the oil film thickness in relation to the level where lubrication is injected, and the lubricant transport will be discussed. The later is of great importance in respect to the oil stress around TDC. Finally, the correlation between the service test and the simulations will be discussed. Investigation of microstructured cylinder liner surfaces for friction reduction Hubertus Ulmer, Leibniz University of Hannover, Germany Friedrich Dinkelacker, Leibniz University of Hannover, Germany Jan Kaestner, Leibniz University of Hannover, Germany Berend Denkena, Leibniz University of Hannover, Germany Christoph Huebsch, Leibniz University of Hannover, Germany Friedrich-Wilhelm Bach, Leibniz University of Hannover, Germany Tim Goettsching, Leibniz University of Hannover, Germany For combustion engines, the specific fuel consumption is significantly affected by friction losses, from which up to 50% can result from the friction of the piston, piston rings and the cylinder. In the consequence of increasing indicated mean effective pressure and maximum cylinder pressure of modern engines, today’s cylinder liner surfaces are exposed to increasing thermal and mechanical loads. To meet these high requirements, the implementation of microstructures is an innovative alternative to adjust the tribological properties. Investigations are presented where innovative microstructured cylinder liner surfaces have been fabricated and evaluated in a research engine. Two approaches have been followed in a joint research group of the Leibniz University of Hannover. In the first approach, microstructures are machined at the Institute of Production Engineering and Machine Tools. Here axially parallel turn-milling strategies were developed and investigated to machine cylinderliners. By defined feed rates and speed ratios, microstructure-patterns and -geometries can be machined continuously. The average dimensions of the microstructures are 1mm to 2mm in length, 50µm to 100µm in width and 5µm to 30µm in depth. To evaluate the tribological characteristics under fired engine conditions, microstructures are implemented in the low- and high-speed areas of fine-honed cylinder liners. The second approach is based on a microstructured surface, being created by a thermal spray process with defined porosity, which is formed at non-melted or resolidified particles between the spray lamellae, and a subsequent honing procedure. With this process, developed by the Institute of Materials Science, microstructured cylinder liner with defined porosity can be created. The coating material is a mixture of FeCr13 and Molybdenum powder. The layer porosity is controlled by adjustable spray parameters such as spraying distance and current. The experimental analysis of the microstructured cylinder liners is carried out at the Institute of Technical Combustion (ITV) on a heavy duty diesel single cylinder research engine. The determination of friction reduction is done with the ’Indication Method’ where the friction mean effective pressure (FEMP) is determined from the difference of the indicated mean effective pressure (IMEP) and the break mean effective pressure (BEMP). Due to precise conditioning of the research engine, additional losses of e.g. valve train and main bearing remain constant, so that the influence of surface structure on friction can be evaluated. One figure in the presentation shows the friction effects (presented as FEMP) during a seven-hour run-in programme for a plateau-honed, a fine-honed and two by machining microstructured cylinder liners. The fine-honed liner shows less friction losses in most of the engine operating points (up to -11%), possibly due to the reduced surface roughness. The liner with a fine-honed ground surface and equipped with microstructures in the TDC area shows significantly lower friction losses (-19% in max.). This can be explained by a higher oil capture capability. The liner with microstructures in the hydrodynamic area shows increased friction losses especially in operating points with higher engine speed. This is presumably an effect of a thicker oil film combined with high piston speeds in the hydrodynamic area of the liner, and therefore increasing stress in the oil film. In summary, cylinder liners with microstructured surfaces show a high potential to reduce friction losses in combustion engines. Currently, oil consumption measurements are carried out in cooperation with the Technical University of Hamburg-Harburg, based on a measurement method that uses a mass spectrometer. Measurement of piston ring lubricant film thickness in a fired engine using ultrasonic reflectometry Phil Harper, Tribosonics Ltd, UK Matthias Stark, Wärtsilä Two-Stroke Engines, Switzerland The lubricating film between piston rings and liners is crucial for correct and continued engine operation. With a worldwide drive to reduce emissions and lubricant consumption in engines, while keeping wear to a minimum, understanding the lubricant film thickness has never been more important. Measurement of lubricant film thickness without disrupting the fluid film has been a significant challenge over the last decades. This paper presents a new technique for measurement of lubricant film thickness based on ultrasonic reflectometry. An ultrasonic sensor is mounted on the back of the component that is to be measured (for example, liner, bearing, piston ring, seal etc). The sensor is excited with a pulse of electrical energy and emits an ultrasonic wave into the components. The ultrasonic wave travels perpendicular to the sensor through the components. When the incident ultrasonic wave interacts with a thin embedded layer (in this case a lubricant film), some of the wave is reflected and some is transmitted. The reflected portion of the wave comes back to the sensor and is converted back to electrical energy. This electrical energy is amplified and acquired by an ultrasonic receiver and digitiser in a PC. The digitised signal is then processed in software to give a measure of the lubricant film thickness. The technique has been applied to a two-stroke diesel engine under fired conditions. Ultrasonic sensors were mounted on the back of the piston ring and connected via cables through a linkage to external electronics. The film thickness over the entire stroke was measured and cyclic variations in the film observed. Results from the experiments are presented and discussed. Ultrasonic reflectometry is demonstrated to be a new technology that has exciting possibilities for many lubricant measurement and monitoring applications. 10 sPeCiaL Schiff&Hafen | Ship&Offshore | May 2013
Monday, May 13th Tuesday, May 14th Wednesday, May 15th Thursday, May 16th Monday May 13th / 15:30 – 17:00 Users´ Aspects Marine Applications – Gas and Emissions Room a Operational experiences of DNV-classed gas-fuelled vessels Thomas Dirix, Det norske Veritas, norway Due to a number of factors, e.g. the increase of the price for fuel oil, air emission regulations and ’pollution taxes’, the number of vessels using LNG as fuel has increased remarkably in the last few years. Many operators of ’gas engine vessels’ have chosen to classify their vessels with Det Norske Veritas, thereby confirming the leading role of DNV in the field of rule development for gasfuelled vessels. The DNV fleet now includes about 30 gas engine driven vessels, having approximately 100 gas engines installed, with contracts for another 40 plus vessels signed. With the oldest engines already in operation for more than ten years, the time seems suitable for an evaluation of experiences with this, after all, relatively young technology and, perhaps, recalibrations of the various applicable regulations. The DNV classified gas engines – both gas only and dual-fuel – are installed on board approximately 30 vessels. These vessels can roughly be divided into three different groups; • Ferries and patrol vessels equipped with gas only engines, • Offshore support vessels operating dual fuel engines on LNG bunkers, • LNG tankers operating dual-fuel engines. Besides the fact that these three groups all have different operating profiles, they also use two different types of gas engines produced by four different engine manufacturers, and, last but not least, different sources of LNG. However, all vessels have in common that they have electric propulsion motors, i.e. all engines are driving generators. This paper will address, with the support of damage statistics, the experiences gained so far by the various operators of gas engines, experiences with both the engines themselves as well as their ancillary systems. In addition, it will investigate to which degree the vessels’ operating profiles and subsequently the engines’ load profiles are of importance for the successful operation of gas engines as generator drivers. Finally, this paper will, based on the experiences inventoried, identify areas where adjustments, or introduction, of regulatory requirements should be considered. LNG as ship’s fuel - Bunkering, storage and processing for medium- and slow-speed engines Juergen Harperscheidt, TGE Marine Gas Engineering GmbH, Germany Shipping is the most eco-friendly means of transportation. Nevertheless, increasingly strict emission regulation as well as high fuel prices create a demand for innovative solutions in ship propulsion. One way to deal with these challenges is the use of LNG as ship’s fuel, thus significantly decreasing emissions of sulphur oxides, particles, NOx and carbon dioxide. All major engine makers have their designs for gas-fuelled or dual-fuel engines available, but in addition to the engines such ships require sys- Do you spend too much time and money on overhaul? CIMAC Booth W4015 Optimize your ship’s engine performance by investing in high quality maintenance machines that will prolong running time and save man-hours. Nor-Shipping Booth E03-27 www.chris-marine.com - info@chris-marine.com - +46 40 671 2600
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